How to Start Seeds Indoors

Jumpstart planting by starting your seedlings indoors, then transplanting into the garden.

By Gail Damerow

| February/March 1993

Sprouting seeds indoors allows you to get a jump on the season for an earlier harvest.PHOTO: MOTHER EARTH NEWS STAFF

Growing plants from seed may seem a bit outmoded. After
all, started seedlings are readily available at every
nursery, as well as many grocery and department stores. But
growing vegetables from seed offers a number of advantages.
For one thing, you'll know exactly what you're growing.
Store-bought seedlings aren't always clearly identified.
For another, your bedding plants will be healthier. Many
Store-bought seedlings have weak, spindly stems and most of
them have gone through extended periods without water. And
then there's the matter of taste. Nearly all of the started
plants you'll find in stores are hybrids, the result of
deliberately crossing two or more plant varieties. Hybrids
are developed to solve the problems of large-scale food
production. They produce larger crops, they ripen all at
once for mechanical harvesting, and they have tough skins
that hold up well during long-distance shipping. Notice
that flavor is nowhere near the top of the list.

We gardeners, on the other hand, like fresh vegetables for
their tenderness and good flavor. We prefer extended
harvests that give us fresh produce over a long period of
time and that don't require marathon canning sessions. In
short, we prefer standard (non-hybrid) varieties. Standards
are rarely available as started plants, but instead must be
grown from seed.

When you start from seed, you have another advantage over
planting seedlings—you can sprout the seeds indoors
to get a jump on the season for an earlier harvest. If your
growing season is short, planting indoors buys time for
slow-growing varieties that otherwise may not mature before
fall's first frost—eggplant, peppers, and tomatoes
among vegetables; impatiens, petunias, and snapdragons
among flowers. And if your climate, like mine, goes too
quickly from frigid to sizzling, cool-weather Cole crops
(cabbage, broccoli, and cauliflower) started indoors can be
handily harvested before the onset of summer heat.

Compared to seeds planted outdoors, those started indoors
have a better germination rate because they're pampered
more. You can enjoy greater variety by planting just a few
pots of several different things, then selecting only the
healthiest plants for transplanting. But the real reason we
die-hard gardeners like to start seeds indoors is that it
lets us get dirt under our fingernails long before the soil
is warm enough or dry enough to garden outdoors.

Getting Started Sprouting Seeds

To start your own indoor nursery, here's what you'll need:

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Seeds. Decide what you want to grow and purchase
the seeds in plenty of time. Mail-order houses offer the
widest variety of seeds, and will supply them when you want
them.

Containers. Those of us who enjoy indoor planting
invariably set up in-house recycle centers tilled with milk
cartons, potato-chip tubes, juice cans, yogurt containers,
and anything else that's at least 3" deep. The best
planting containers are either tapered—like yogurt
containers—so plants can easily be slipped out, or
are made of paper-like milk cartons and juice cans—so
they can be torn open for plant removal. Flats (shallow
trays) may offer more planting space than individual pots,
but you're more likely to disturb tender roots at
transplant time.

To prepare containers for planting, wash them well, rinse
in warm water laced with a little chlorine bleach, and dry
them in the sun. With a nail, poke one or more small
drainage holes in the bottoms of all containers so you
won't drown your seedlings. If money is no object, save
yourself the bother of cleaning containers by buying pots
designed specifically for sprouting seeds. Seedlings
started in pots of pressed fiber or peat can be planted in
the garden, pot and all. Some seed —starting kits
come with their own planting mix.

Planting mix. Seeds sprout best in soil that
drains well, that doesn't easily compact, and that's free
of competing weed seeds, fungi, and other organisms that
can disease young plants. Sterile planting mixes, available
at any garden center, are relatively inexpensive. If you
buy a mix containing soil, be sure the label says it's been
sterilized.

Most mixes blended especially for germinating seeds contain
no soil at all, but are a mixture of sphagnum moss
(decomposed moss mined from swamps), perlite (a form of
volcanic ash), and vermiculite (mica expanded with heat,
like popcorn). This blend holds water well, but is
difficult to initially moisten. To dampen it sufficiently
for planting, put some into a plastic bag, add water, and
knead. Because this mixture is low in nutrients, you'll
have to fertilize seedlings from the time they achieve
three weeks' growth, using half the strength solution you'd
use for mature plants.

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If you run out of planting mix at a crucial moment, or you
prefer not to spend money on someone else's mix, you can
make your own by combining equal parts sphagnum moss
(available from most garden centers), sifted compost, and
sifted garden soil. To eliminate soil-borne organisms that
cause plant problems, pasteurize the sifted soil and
compost by lightly moistening it and heating it in a
180°F oven for 45 minutes. Since cooking soil doesn't
exactly smell like freshbaked bread, place the mix in a
broiler bag (of the sort you'd use to cook a turkey) and
spread it on a shallow tray. Stir in the sphagnum moss and
cool well before planting.

Labels. Since newly sprouted plants look pretty
much alike, labels will help you keep track of what's what.
If something doesn't come up and needs replanting, you
won't have to guess what it was. You can buy bona fide
nursery labels, save up popsicle sticks, or make labels by
cutting a liquid bleach container into 1/2" vertical strips
and trimming a point at one end. Some planting containers
(like containers from yogurt, cottage cheese, and sour
cream) are easy to write on with an indelible marker,
eliminating the need for separate labels.

Light. Plants started in a window sill soon grow
leggy and topple over—perhaps because, at this time
of year, the sky stays cloudy for days on end. A light for
your seedlings therefore makes a good investment and can be
used year after year. You might enjoy the prestige (and
expense) of a specially designed "grow" light, but you'll
get the same good results with inexpensive fluorescent
tubes and a fixture from the local discount store.

Cool white ("daylight") 40-watt tubes throw even light of
the sort plants thrive on, and they don't get hot enough to
burn tender leaves. Select a fixture (or combination of
fixtures) that's the right size to cover all your pots,
placed directly below the light. Hang the fixture from
chains so that you can raise it as plants grow, keeping the
light about 1" above plant tops.

Warmth. Most seeds germinate best in a warm,
draft—free place. Where the temperature is a little
high, plants will grow fast and become leggy. Where the
temperature is a little low, plants will grow slowly and
have strong, sturdy stems; however, if the temperature is
too low, seeds won't germinate at all. If the area where
you plan to start your seeds is much cooler than 70° to
75°F, find a warm place such as the top of the water
heater or refrigerator. After the seeds germinate, place
the pots under the light.

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Planting Seeds

Now all you need to know is the date of the last expected
frost in your area. If you aren't sure, call your county's
agricultural extension office. Start seeds for slow-growing
plants like cabbage, eggplant, head lettuce, peppers, and
tomatoes eight weeks before the last-frost date. Start
fast-growing plants like Chinese cabbage, cucumbers,
melons, pumpkins, and squash four weeks before the last
frost. You don't want fast-growing plants to outgrow their
pots and get root-bound while you wait for your garden soil
to warm up or dry out enough for transplanting. As a
general rule, it's better to start seeds a little too late
than a little too early.

Fill each container with planting mix to within V," of the
top. Press the mix gently to firm it up without packing it
solid. In each container, arrange two large seeds (such as
cucumber, squash, or pumpkin) or three small seeds (such as
tomato or cabbage). If small seeds stick to your fingers
and are hard to place, pick them up with tweezers.

Cover large seeds with soil to no more than three times
their thickness. Press small seeds into the soil without
covering them, since otherwise they might get buried too
deeply to germinate. To avoid washing the planting mix away
from the seeds, water the pots with a spray bottle filled
with warm water. To keep the soil from drying out, lay a
piece of newspaper across the tops of the containers.

Water the pots daily, taking care to not let the soil get
too soggy or dry. Different seeds take different amounts of
time to germinate. The label on your seed packets should
tell you the germination times for the varieties you plant.
As soon as little green sprouts appear, remove the
newspaper and turn on the grow light. Turn the light off
each night to give plants a rest. Continue watering daily
so soil stays evenly moist.

When plants have four true leaves (not counting those first
nondescript round leaves all plants start out with), thin
plants to one per pot. Don't pull out the weak plants or
you'll disturb the roots of the remaining plant. Instead,
use scissors to snip off all but the strongest single plant
in each pot. Water a little less often from now on,
allowing the soil's surface to dry out between waterings.

Transplanting Seedlings

Before your plants get big enough for the great outdoors,
they should be transplanted into larger pots at least once.
Transplant peppers and tomatoes twice. Any plant needs
transplanting if it outgrows its pot while you're waiting
for conditions outside to be right for the big move.
Putting plants in bigger pots stimulates root growth,
thanks to new soil with fresh nutrients and greater room
for roots to spread.

Whenever you transplant a seedling, make sure to thoroughly
water it first. Then run a butter knife around the edge of
the pot to loosen the root ball. Hold the pot in one hand
and tip it upside down onto your other hand, so the root
ball lands on your fingers and the plant falls between
them. (If you planted in fiber or peat pots, break away the
bottom so roots can get through, then replant the pot and
all.) Add enough planting mix to bury the stem up to the
first true leaves. Press the mix firmly around roots and
then water the plant once more. Transplants may droop but
should grow upright within a day or two.

When the time comes to move your plants outdoors, avoid an
abrupt move that will shock them and retard their growth.
Instead, let your plants gradually adjust to being outside
through a process called "hardening off." One week before
transplant time, place the seedlings outdoors in a shady
spot that's protected from any wind. If the nights are
still cool, bring the plants inside before the sun goes
down. Gradually move the plants until they're getting full
sun during the day. (Watch that the sun or wind doesn't dry
them out—you may have to water more often than you
have been.)

Cool-weather varieties such as sole crops may be moved to
the garden as soon as the soil can be worked and the danger
of heavy frost is over. Warm-weather plants like tomatoes
shouldn't go out until all danger of frost has past.

Saving Seeds

If you have seeds left over, they will keep for at least a
year. Some can be stored for up to five years, provided you
keep them in airtight containers in a cool, dry place.

You might even save seeds from plants you grow yourself,
provided that they're standards rather than hybrids.
Hybrids cannot be grown from seeds you gather yourself, but
must be purchased year after year (another reason
commercial growers favor them). If you harvest seeds from a
hybrid, they will not grow true to the parent plant.
Instead, they'll likely either be sterile or will revert to
one or another of the plants in their background.

Standard varieties grow true to type as long as they have
not inadvertently been crossed with related plants growing
nearby. Saving your own seeds gives you a certain sense of
satisfaction, as well as a modicum of self-sufficiency. It
also helps preserve old-time varieties. Of the vegetables
cataloged by the USDA in 1902, only 3% still exist today.
The rest have been replaced by hybrids.

Protecting Transplants

The best time to move seedlings to the garden is on a warm,
windless, cloudy day when light showers are predicted.
Unfortunately, the weather doesn't always cooperate. Chilly
nights, not to mention the drying effects of wind and sun,
can quickly wipe out all those little plants you tended so
carefully.

Garden centers carry protective devices, called "hotcaps,"
of every shape, size, and especially price. To save money,
you can protect seedlings with large mills cartons,
inverted cans, or anything else big enough not to touch a
plant's leaves. Hotcaps hold in heat during the night, but
in sunny weather they must be removed during the day so
they won't collect the sun's heat, cooking new transplants.

If you've got lots of little plants, setting out hotcaps
each evening and gathering them up each morning gets to be
a hassle. And while the hotcaps are off, seedlings have no
protection from wind and unrelenting sun. Pondering these
problems, my husband and I hit on the idea of fashioning
plant protectors from white plastic trash-bag liners. We
slit the bottoms open and cut each 20" by 28.5" liner into
three 20" x 9.5" strips. We used our food-pouch heat sealer
to form tubular pockets along the two folds. Into the
tubular pockets we slipped two slender stakes, which we
poked into the ground as an anchor.

We used a third stake to pull the plastic out into a right
angle corner, creating a protector with two walls oriented
to shield a plant from both sun and wind. In seasons when
the wind whipped around from several directions, we opened
up the plastic and added a fourth stake to create a box
with four walls. 'these plastic protectors could be reused
several times in one season, but they don't hold up well
enough to be stored for future seasons. To us, that seemed
a tad wasteful.

So we looked around for something that could be saved year-
after year and discovered fiberglass sheeting, a recycled
product left over from the manufacture of paper and used to
shield gamebirds from wind. The fiberglass comes in rolls
of various widths—the 2' roll turned out to be ideal
for protecting plants.

Using scissors, we cut the fiberglass into 1' strips,
fashioned each strip into a 1' high tube stapled to two
wooden stakes. When the stakes are pushed into the ground
on either side of a plant, the tube surrounds the plant and
protects it from all directions. The white fiberglass does
not collect and hold excess heat, and is porous enough to
allow air movement but not drafts.

Fiberglass is durable and does not rot or rip. The
protectors can easily be threaded onto a length of rope and
hung from the rafters of a storage shed. A 2' wide roll
containing 100 feet costs $30, but you can buy only as much
as you need.

Both the one-season plastic protectors and the more durable
fiberglass kind will keep plants warm throughout the night
unless unseasonable frost threatens. In that case, slip a
paper bag over each protector late in the afternoon, before
the sun goes down. In blowing wind, put a small stone or
dirt clot on each bag to keep it from blowing away. Avoid
trapping excess heat by removing bags in morning soon after
the sun comes up.

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